<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <p id="text">hello world</p>
    <script>
        // var p = document.getElementById('text')
        // p.style.color = 'red'

        var a = 10  // var、a、= 2
        
        function foo(a){
            var b = 2

            function bar(){
                console.log(4);
            }
            var c = 3
        }
        foo(1)
        console.log(a,b,c);

        // ['var','a','='.
    </script>
</body>
</html>